The present invention generally relates to fixing units and image forming apparatuses, and more particularly to a fixing unit which is constructed to clean a fixing heat roller, and to an image forming apparatus which improves the quality of an image formed on a medium by improving cleaning of the fixing heat roller, preventing scattering of a toner within an image forming unit or preventing solidification of a developing agent which is supplied to the image forming unit.
Recently, image forming apparatuses employing electrostatic recording are used as printers and copying machines, and color images are also formed on mediums such as paper. However, according to the image forming apparatus employing the electrostatic recording, a developing agent including a toner is used. For this reason, when the toner or the developing agent adheres on parts of the image forming apparatus or is scattered, the toner or developing agent that is adhered or scattered interferes with the operation of the parts and stains the medium, thereby deteriorating the quality of the image formed on the medium. In addition, when the developing agent is stored for a long period of time, the developing agent solidifies and it becomes difficult to bring out the original performance of the developing agent and the image forming apparatus. Accordingly, there are demands to realize an image forming apparatus which can form the image on the medium with an improved quality, by taking measures such as positively cleaning the stain adhered on the parts of the image forming apparatus, preventing the toner from scattering and adhering on the parts of the image forming apparatus, and preventing solidification of the developing agent.
Conventionally, as methods of cleaning the fixing heat roller of the fixing unit, there is a method which uses a felt pad, and a method which uses a cleaning member which is often referred to as a frieze. According to the method which uses the felt pad, the felt pad constantly makes contact with the surface of the fixing heat roller so as to remove the toner or the like adhered on the surface of the fixing heat roller. For this reason, the cleaning capability greatly deteriorates when the felt pad becomes stained, and it is necessary to replace the felt pad relatively frequently.
On the other hand, according to the method which uses the frieze, a supply reel and a take-up reel are provided for the frieze, and the frieze makes contact with the surface of the fixing heat roller between the supply and take-up reels. Hence, the cleaning surface of the frieze constantly changes by driving the take-up reel. As a result, the cleaning capability of the frieze is always high, and the replacement intervals of the frieze is relatively long compared to that of the felt pad.
In an image forming unit which transfers a toner image onto the medium, the toner is easily scattered from an end portion of a transport roller which transports the developing agent to a developing roller. When the toner enters a bearing portion or a rotary drive portion of the transport roller, the rotary performance of the transport roller greatly deteriorates, and the transport of the developing agent to the developing roller becomes unstable, thereby deteriorating the quality of the image that is finally formed on the medium. Hence, proposals have conventionally been made to suppress the scattering of the toner by providing a sealing member at the end portion of the transport roller.
In addition, when the developing agent within the image forming unit is additionally supplied or changed, it is not only time consuming and troublesome for the user to manually supply the developing agent to the image forming unit, but the user's hands, the image forming apparatus and the periphery of the image forming apparatus are easily stained by the developing agent. Hence, an image forming apparatus has been proposed in which a hopper is provided to supply the developing agent to the image forming unit. In this proposed image forming apparatus, the developing agent stored within the hopper is supplied to the image forming unit by manually or automatically opening a lid of the hopper.
However, according to the method which uses the frieze, there were problems in that a driving source is required exclusively for driving the take-up reel and that the construction of the image forming apparatus is complex.
In addition, although no particular mechanisms have been proposed, a proposal has been made to drive the take-up reel by a mechanism which reduces the rotation of the fixing heat roller. But if the take-up reel were driven by the mechanism which reduces the rotation of the fixing heat roller, the frieze would be used up in a relatively short time because the take-up reel would be driven continuously. It is necessary to rotate the take-up reel extremely slowly compared to the fixing heat roller in order to reduce the amount of frieze that is used up, however, a mechanism which greatly reduces the rotation of the fixing heat roller would become quite bulky and complex, and the use of such a mechanism was not practical particularly in the image forming apparatus or the like which needed to be compact.
On the other hand, in the image forming apparatus which is provided with the sealing member at the end portion of the transport roller within the image forming unit in order to suppress the scattering of the toner, it is necessary to mount the sealing member on the transport roller. In this case, there was a problem in that the operation of mounting a ring-shaped sealing member on the transport roller is difficult to perform. In addition, when mounting a band-shaped sealing member on the transport roller, there was a problem in that ends of the band-shaped sealing member may overlap or a gap may be formed between the ends of the band-shaped sealing member. If the ends of the band-shaped sealing member overlap, the rotatory performance of the transport roller deteriorates and the scattering of the toner easily occurs through portions of the band-shaped member other than the ends thereof. On the other hand, if the gap is formed between the ends of the band-shaped sealing member, the scattering of the toner easily occurs through the gap.
Furthermore, in the case of the image forming apparatus provided with the hopper which supplies the developing agent to the image forming unit, the developing agent stored within the hopper easily solidifies, and there was a problem in that the developing agent may not be supplied to the image forming unit even when the lid of the hopper is opened.